io - Heavy replication write load on MySQL slave -

we using percona mysql 5.6 on debian 8 ecommerce aggregator. there master backend server doing whole etl (processing product feeds partners) , slave mysql server used frontend web servers. it's single product database 600gb data.

both machines have raid10 datacenter series ssds. master mysql dual xeon e5 128gb ram , slave single xeon e5 64gb ram. our problem is, etl i/o heavy (with thousands of iops), master able handle i/o load slave server cannot keep replication. work done in ramdisk , real neccessary data written database, already.

the slave has more reads writes, replication cannot catch up. options there scaling replication writes (i.e. i/o load) on slave?

edit 2016-11-18: "options" i'm not asking optimizing mysql, other techniques or software handle situation better.

upgrading 5.7 should solve immediate problem: http://mysqlhighavailability.com/multi-threaded-replication-performance-in-mysql-5-7/.

this precursor master running out of write capacity. should start thinking sharding soon. can check out youtube's vitess.io project, i'm part of.